# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def mirror(self, root):
        """
        :type root: TreeNode
        :rtype: void
        """
        if root == None:
            return None
        else:
            if root.left == None and root.right == None:
                a = 1
            elif root.left != None and root.right == None:
                self.mirror(root.left)
                root.left, root.right = root.right, root.left
            elif root.left == None and root.right != None:
                self.mirror(root.right)
                root.left, root.right = root.right, root.left
            else:
                self.mirror(root.left)
                self.mirror(root.right)
                root.left, root.right = root.right, root.left